1. Field of the Invention
The present invention relates to a liquid crystal gel, gelling agent, liquid crystal device, and a process for fabricating a liquid crystal device. More particularly, the present invention relates to a liquid crystal gel with substantially no fluidity, a gelling agent capable of easily producing the liquid crystal gel, a liquid crystal device made from the liquid crystal gel with substantially no fluidity, and a process for fabricating a liquid crystal device capable of providing this liquid crystal device rapidly in a simple manner.
2. Description of the Background Art
In recent years, liquid crystal devices (liquid crystal displays) including a light adjusting layer are enjoying wide popularity due to the advantage that a polarizing plate and orientation processing are not required to obtain superior brightness and clear contrast. In these types of liquid crystal devices, liquid crystal molecules are generally used as a material for the light adjusting layer. However, the liquid crystal molecules alone are not sufficient to satisfy a high-speed response which is increasingly demanded for the liquid crystal devices.
Because of this, a high polymer dispersion-type liquid crystal has been proposed. This high polymer dispersion-type liquid crystal principally has a structure with liquid crystal molecules distributed in a polymer wherein the optical transmission mechanism is thought to be of a light scattering mode which ensures more rapid response than individual use of liquid crystal molecules.
The high polymer dispersion-type liquid crystal is typically manufactured by polymerization method. Specifically, two sheets of substrate with an electrode, at least one of the sheets being transparent, for example, glass plates with an indium tin oxide film as an electrode formed thereon, are provided. A photopolymerizable monomer, as a liquid polymeric raw material, and liquid crystal molecules are introduced between the two sheets. Then, the photopolymerizable monomer is exposed to ultraviolet radiation or the like through the transparent substrate to induce polymerization, thereby producing a high polymer dispersion-type liquid crystal in which liquid crystal molecules are dispersed inaphotopolymerized high polymer (see, for example, Japanese Patent Applications Laid-open No. 340587/1994, No. 17910/1995, and No. 69983/1995).
However, this conventional process requires different materials which are the photopolymerizable monomer and the liquid crystal molecules to be introduced into a narrow space between the two sheets of substrate during the process for fabricating the liquid crystal device. It is difficult to introduce a liquid such as a liquid crystal into a narrow space between the two sheets of substrate homogeneously without causing air bubbles to be entrapped. In addition, such a procedure extends the period of time required for manufacturing and causes the production process to become complicated.
Moreover, it is not easy to uniformly polymerize a photo-polymerizable monomer by ultraviolet radiation process. An additional problem is the difficulty in homogeneously mixing of the resulting polymer and the liquid crystal molecules.
Moreover, in order to maintain an accurate distance between two sheets of substrate, a spacer is added in a high polymer dispersion-type liquid crystal.
Still another problem is that the low viscosity of the liquid photo-polymerizable monomer and liquid crystal molecules makes it difficult to homogeneously disperse a spacer which is usually added to a high polymer dispersion-type liquid crystal to accurately maintain the distance between the two sheets of substrate.
In addition, when a photo-polymerizable monomer is used, it is necessary to provide an exposure step after introducing the photo-polymerizable monomer and liquid crystal molecules into the space between the two sheets of substrate. This requires a special exposure device, extending the manufacturing time, and makes the production process complicated.
In addition, when the liquid crystal device having a high polymer dispersion-type liquid crystal as a light adjusting layer is used for a decorative display plate such as an advertising plate, a display for a clock or an electric calculator, a display requiring a bright screen, particularly a display for a computer terminal, a display for a projection, or the like, such a device (a) must be driven by a sufficiently low voltage using a drive circuit which is commonly used at present and (b) must exhibit reduced hysteresis (a phenomenon in which the light transmittance shows different values during voltage increase and voltage decrease) which may result in a decrease of a time split drive margin and produce a problem in performing a gradation display.